The growing shortage of a fresh water supply in many areas, as well as a world-wide concern with the environment, makes it imperative that fresh water resources be used as wisely as possible. However the common flush toilet in use in western countries today uses approximately 21/2 gallons of fresh water per flush. A household of four people under normal conditions can be expected to flush between 50 and 60 gallons of clean, fresh water down the toilet each day. A normal bath or shower will use an average about 15 gallons of clean fresh water per use, more or less, depending on the individual. Multiply this use by the number of persons in a multistory building, and it is clear that a very large volume of clean, fresh water is used in each such building. In an urban environment all of this clean fresh water must be purified or otherwise treated, which is costly.
Several patents have issued describing inventions relating to recycling of waste water for the purpose of flushing toilet waste.
For example, U.S. Pat. No. 4,115,879 to Tom, U.S. Pat. No. 3,318,449 to Jennings, and U.S. patent to Kimball describe systems in which waste water is recovered from a variety of sources, such as bathtubs, showers, sinks, washing machines, etc. and store waste water in large holding tanks. However in each of these cases, pumps are required. In addition, strong detergents are present in the waste water due to their sources. These can clog and corrode the pumps.
These systems also require large holding tanks and extensive new plumbing lines. These systems would be extremely expensive and very difficult to retrofit into existing buildings. They also require a considerable amount of space and are not suitable for use in apartment buildings, hotels and similar buildings.